Motion vector correction device and method and video signal processing apparatus and method

ABSTRACT

A motion vector detector detects, using pixel data in at least two real frames in an input video signal, a motion vector MV 1  necessary for generating interpolated pixel data forming an interpolated frame to be inserted between the two real frames. A motion vector corrector corrects the motion vector MV 1  to decrease the magnitude of motion vector MV 1  when the magnitude of motion vector MV 1  exceeds a predetermined threshold, and outputs it as a motion vector MV 3.

This is a National Phase Application filed under 35 U.S.C. 371 as anational stage of PCT/JP2011/055520 filed Mar. 9, 2011, and claimspriority from Japanese Application No. 2010-110962, filed May 13, 2010,the content of each of which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to a motion vector correction device andmethod and a video signal processing apparatus and method capable ofreducing a feeling of visual strangeness in an interpolated image due toa false detection of motion vector.

BACKGROUND ART

When an image display apparatus displays a moving image on a liquidcrystal panel thereof, a motion blur occurs frequently in the movingimage. In order to reduce a motion blur, an interpolated frame isinserted between real frames in a video signal to increase the number offrames. For example, a frame rate of 60 Hz in a vertical frequency isconverted into 120 Hz or more. Then an image display is carried out. Inorder to carry out a frame rate conversion, a video signal processingapparatus detects a motion vector in an image and generates eachinterpolated pixel based on the motion vector to obtain an interpolatedframe to be inserted between real frames.

A motion vector is generated based on pixel data within a limited rangein respective limited frames (e.g., successive two frames). Thus, it isdifficult to completely eliminate a false detection of motion vector. Inview of the above-described problem, technical improvements for reducinga false detection of motion vector are carried out. As one example,Patent document 1 discloses a frame rate conversion apparatus providedwith a motion vector detection device capable of reducing a falsedetection of motion vector.

CITATION LIST Patent Literature

Patent document 1: Japanese Patent Application Laid-open Publication No.2006-331136

SUMMARY OF INVENTION Technical Problem

In a video signal processing apparatus provided with a motion vectordetection device, it is required to reduce a feeling of visualstrangeness in an interpolated image due to a false detection of motionvector. In particular, in a case where a detected motion vector isrelatively large, when a false detection occurs, a feeling of visualstrangeness in an interpolated image is remarkably enhanced.

The present invention is made in view of the above-described problem andhas an object to provide a motion vector correction device and methodand a video signal processing apparatus and method capable of reducing afeeling of visual strangeness in an interpolated image even when a falsedetection occurs in a case where a motion vector is relatively large.

Solution to Problem

In order to resolve the above-described conventional technical problem,the present invention provides a motion vector correction deviceincluding: a motion vector detector (2) that, using pixel data in atleast two real frames in an input video signal, detects a first motionvector necessary for generating interpolated pixel data forming aninterpolated frame to be inserted between the two real frames; and amotion vector corrector (4) that corrects the first motion vector todecrease the magnitude of first motion vector when the magnitude offirst motion vector exceeds a first threshold.

In the above-described configuration, the motion vector correctorincludes: a motion vector value suppressing part (41) that decreases themagnitude of first motion vector exceeding the first threshold at apredetermined rate, and outputs the result as a second motion vector;and a motion vector value converting part (42) that decreases themagnitude of second motion vector to prevent the magnitude of secondmotion vector from increasing when the magnitude of second motion vectorexceeds a second threshold, and outputs the result as a third motionvector.

As a preferable embodiment, the motion vector value suppressing partcalculates the second motion vector according to the following calculusequation(the magnitude of first motion vector)×m/n+(the firstthreshold)×(n−m)/n,

where variables m and n are natural numbers which have a relation ofm<n.

The motion vector value converting part holds the magnitude of thirdmotion vector constant within a range in the magnitude of second motionvector from the second threshold to a third threshold more than thesecond threshold, and decreases the magnitude of third motion vector ata predetermined rate when the magnitude of second motion vector exceedsthe third threshold.

As a preferable embodiment, when the magnitude of second motion vectorexceeds the third threshold, the motion vector value converting partcalculates the third motion vector according to the following calculusequation2×(the second threshold)+(the third threshold−the second threshold)−(themagnitude of second motion vector).

It is preferable to further include a motion vector state determiner (3)that determines an appearance state of the first motion vector in ascreen to generate and output a state determination value, wherein themotion vector corrector varies characteristics of decrease of themagnitude of first motion vector according to the state determinationvalue.

As a preferable embodiment, the motion vector state determiner generatesa state determination value that represents an appearance amount ofmotion vectors indicating how many first motion vectors appear in ascreen. As another preferable embodiment, the motion vector statedeterminer generates a state determination value that represents adistribution state of motion vectors indicating a degree of uniformityor variation of directions of first motion vectors in a screen.

In order to resolve the above-described conventional technical problem,the present invention provides a video signal processing apparatusincluding: an interpolated pixel data generator (5) that generatesinterpolated pixel data, using pixel data in at least two real frames inan input video signal and a motion vector corrected by any one of theabove-described motion vector correction devices.

Also, in order to resolve the above-described conventional technicalproblem, the present invention provides a motion vector correctionmethod including: a motion vector detection step for, using pixel datain at least two real frames in an input video signal, detecting a firstmotion vector necessary for generating interpolated pixel data formingan interpolated frame to be inserted between the two real frames; and amotion vector correction step for correcting the first motion vector todecrease the magnitude of first motion vector when the magnitude offirst motion vector exceeds a first threshold.

The motion vector correction step includes: a motion vector valuesuppressing step for decreasing the magnitude of first motion vectorexceeding the first threshold at a predetermined rate, and outputtingthe result as a second motion vector; and a motion vector valueconverting step for decreasing the magnitude of second motion vector toprevent the magnitude of second motion vector from increasing when themagnitude of second motion vector exceeds a second threshold, andoutputting the result as a third motion vector.

As a preferable embodiment, the motion vector value suppressing stepcalculates the second motion vector according to the following calculusequation(the magnitude of first motion vector)×m/n+(the firstthreshold)×(n−m)/n,

where variables m and n are natural numbers which have a relation ofm<n.

The motion vector value converting step holds the magnitude of thirdmotion vector constant within a range in the magnitude of second motionvector from the second threshold to a third threshold more than thesecond threshold, and decreases the magnitude of third motion vector ata predetermined rate when the magnitude of second motion vector exceedsthe third threshold.

As a preferable embodiment, when the magnitude of second motion vectorexceeds the third threshold, the motion vector value converting stepcalculates the third motion vector according to the following calculusequation2×(the second threshold)+(the third threshold−the second threshold)−(themagnitude of second motion vector).

It is preferable to further include a motion vector state determinationstep for determining an appearance state of the first motion vector in ascreen to generate a state determination value, wherein the motionvector correction step varies characteristics of decrease of themagnitude of first motion vector according to the state determinationvalue.

As a preferable embodiment, the motion vector state determination stepgenerates a state determination value that represents an appearanceamount of motion vectors indicating how many first motion vectors appearin a screen. As another preferable embodiment, the motion vector statedetermination step generates a state determination value that representsa distribution state of motion vectors indicating a degree of uniformityor variation of directions of first motion vectors in a screen.

In order to resolve the above-described conventional technical problem,the present invention provides a video signal processing methodincluding: an interpolated pixel data generation step for generatinginterpolated pixel data, using pixel data in at least two real frames inan input video signal and a motion vector corrected by any of theabove-described motion vector correction methods.

Advantageous Effects of Invention

According to the motion vector correction device and method and thevideo signal processing apparatus and method of the present invention,in a case where a motion vector is relatively large, even when a falsedetection occurs, it is possible to reduce a feeling of visualstrangeness in an interpolated image.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 It is a block diagram that shows one exemplary embodiment of thepresent invention.

FIG. 2 It is a diagram that illustrates a first example of operation ofa motion vector state determiner 3 in FIG. 1.

FIG. 3 It is a diagram that illustrates a second example of operation ofthe motion vector state determiner 3 in FIG. 1.

FIG. 4 It is a block diagram that shows a concrete configuration exampleof a motion vector corrector 4 in FIG. 1.

FIG. 5 It is a diagram that illustrates operation of a motion vectorvalue suppressing part 41 in FIG. 4.

FIG. 6 It is a diagram that illustrates operation of a motion vectorvalue converting part 42 in FIG. 4.

FIG. 7 It is a diagram that illustrates a first example of operation ofthe motion vector corrector 4 in FIG. 1.

FIG. 8 It is a diagram that illustrates a second example of operation ofthe motion vector corrector 4 in FIG. 1.

FIG. 9 It is a diagram that illustrates a third example of operation ofthe motion vector corrector 4 in FIG. 1.

DESCRIPTION OF EMBODIMENTS

A motion vector correction device and method and a video signalprocessing apparatus and method will be described below with referenceto the drawings. As one example of a video signal processing apparatus,one exemplary embodiment of the present invention shown in FIG. 1illustrates a frame rate conversion apparatus that inserts aninterpolated frame between real frames in a video signal to convert aframe rate two times. The frame rate conversion apparatus may convert aframe rate three times or more. Although the video signal processingapparatus of the present invention is not limited to the frame rateconversion apparatus, it may be a film judder elimination apparatusprovided with a motion vector detection device. The present invention isapplicable to any video signal processing apparatus provided with amotion vector detection device.

In FIG. 1, pixel data in a video signal Sin having a frame frequency of60 Hz is sequentially input into a frame memory 1, a motion vectordetector 2, an interpolated pixel data generator 5 and a frame frequencyconverter 6. The frame memory 1 delays input pixel data by one frame andoutputs it. A symbol “F0” is defined as a current frame of input videosignal Sin. A symbol “F1” is defined as a frame which is one frame priorto the current frame output from the frame memory 1. The current frameF0 and the frame F1 are real frames. Pixel data in the frame F1 issequentially input into the motion vector detector 2 and theinterpolated pixel data generator 5.

The motion vector detector 2 detects a motion vector MV1 to be used togenerate interpolated pixel data in an interpolated frame to be insertedbetween the current frame F0 and the frame F1, using two pieces of pixeldata in the current frame F0 and the frame F1 according to a matchingmethod, for example. The motion vector MV1 may be detected in a pixeldata unit or a block unit composed of plural pieces of pixel data. Themotion vector detector 2 includes plural line memories, a pixel delaypart, a subtraction part that calculates a difference of two pieces ofpixel data and the like (not shown). The motion vector MV1 is input intoa motion vector state determiner 3 and a motion vector corrector 4. Themotion vector MV1 may be detected using a past frame prior to the frameF1, in addition to the current frame F0 and the frame F1.

The motion vector state determiner 3 determines a motion vector state ineach frame and then outputs a determination signal D1. Concreteoperation of the motion vector state determiner 3 will be describedlater in detail. The determination signal D1 is input into the motionvector corrector 4. The motion vector corrector 4 corrects the motionvector MV1 such that the magnitude of motion vector MV1 is decreasedaccording to the determination signal D1, and then outputs it as amotion vector MV3. Concrete configuration and operation of the motionvector corrector 4 will be described later in detail. The motion vectorMV3 is input into the interpolated pixel data generator 5.

The interpolated pixel data generator 5 includes plural line memoriesand a pixel delay part (not shown) used to delay pixel data in thecurrent frame F0 in a horizontal direction and a vertical direction andgenerate pixel data within a certain range of the current frame F0 inthe horizontal direction and the vertical direction, and plural linememories and a pixel delay part (not shown) used to delay pixel data inthe frame F1 in a horizontal direction and a vertical direction andgenerate pixel data within a certain range of the frame F1 in thehorizontal direction and the vertical direction. The interpolated pixeldata generator 5 further includes an averaging part that selects pixeldata in the current frame F0 and pixel data in the frame F1 according tothe motion vector MV3 and averages them to generate interpolated pixeldata.

In the present embodiment, although the interpolated pixel data isgenerated using two pieces of pixel data in two real frames, theinterpolated pixel data may be generated using three pieces of pixeldata or more in three real frames or more.

Pixel data in the frame F0 and interpolated pixel data from theinterpolated pixel data generator 5 are sequentially input into theframe frequency converter 6. The frame frequency converter 6 may becomposed of a time series conversion memory. The frame frequencyconverter 6 generates image data of the frame F0 which is a real framebased on the pixel data in the frame F0 sequentially input, and imagedata of an interpolated frame F1 which is an interpolated frame based onthe interpolated pixel data sequentially input from the interpolatedpixel data generator 5.

Then, the frame frequency converter 6 alternately selects the image dataof the frame F0 and the image data of the interpolated frame Fi at afrequency of 120 Hz, and outputs a video signal Sout with a framefrequency of 120 Hz.

The concrete operation of the motion vector state determiner 3 will bedescribed below. First, a first example of the operation of the motionvector state determiner 3 will be described with reference to FIG. 2.FIG. 2 conceptually illustrates operation carried out in the firstexample. The motion vector state determiner 3 segments a screen of oneframe into plural regions. The number of segmented regions into which ascreen of one frame is segmented may be arbitrarily determined. FIG.2(A) shows a segmented region AR. Plural pixels are included in thesegmented region AR. The number of pixels included in the segmentedregion AR is dependent on the number of segmented regions AR. In onecase of detecting the motion vector MV1 in a pixel data unit, pluralmotion vectors MV1 of which the number is equal to the number of pixelsin the segmented region AR appear. In another case of detecting themotion vector MV1 in a block unit composed of plural pieces of pixeldata, plural motion vectors MV1 of which the number is equal to thenumber of blocks in the segmented region AR appear.

The motion vector state determiner 3 determines whether or not a motionvector MV1 appears at every detection unit of motion vector MV1 in thesegmented region AR, and sets “1” if the motion vector MV1 appears orsets “0” if the motion vector MV1 does not appear. Then, the motionvector state determiner 3 counts the number of appearances of motionvectors MV1 by summing “1” in the segmented region AR. When the numberof appearances of motion vectors MV1 (count value) exceeds apredetermined threshold, the motion vector state determiner 3 assigns“1” to the segmented region AR as a determination value for segmentedregion, as indicated at the right side of an arrow in FIG. 2(A). Whenthe number of appearances of motion vectors MV1 does not exceed thepredetermine threshold, the motion vector state determiner 3 assigns “0”to the segmented region AR as a determination value for segmentedregion. For example, half the number of detection units is set as athreshold, and when the number of appearances of motion vectors MV1exceeds half the number of detection units, “1” is assigned.

FIG. 2(B) shows a state of assigning a determination value for segmentedregion “0” or “1” to each of segmented regions AR00, AR01, AR02, AR03 .. . , AR10, AR11, AR12, AR13 in the screen. The motion vector statedeterminer 3 counts the number of segmented regions AR each to which adetermination value for segmented region “1” is assigned, by summingdetermination values for segmented regions assigned to all segmentedregions AR in the screen. Then, the motion vector state determiner 3outputs a determination signal D1, which represents one of eight-levelstate determination values of “0” to “7” for example, according to thecount value.

As described above, in the first example of the operation of the motionvector state determiner 3, the determination signal D1 which representshow many motion vectors MV1 appear in one frame (screen) is generated.That is, in the first example, the determination signal D1 whichrepresents the number of appearances of motion vectors MV1 in one frameis generated without consideration of a direction of motion vector MV1.The state determination value increases as the number of appearances ofmotion vectors MV1 increases. A large state determination valueindicates that the motion vectors MV1 stabilize.

Next, a second example of the operation of the motion vector statedeterminer 3 will be described with reference to FIG. 3. FIG. 3conceptually illustrates how a motion vector MV1 appears every adetection unit of motion vector MV1 in one frame. A black circleindicates a state (motion “0”) where a motion vector MV1 is not detectedand corresponds to a value “0” in a matrix at the left side of the arrowin FIG. 2(A). In the example of FIG. 3, a motion vector MV1 directed toa right direction, a motion vector MV1 directed to an upper direction,and a motion vector MV1 directed to an upper right direction appear, aspointed by respective arrows.

The motion vector state determiner 3 determines how motion vectors MV1are distributed in one frame. As one example, motion vectors MV1 areclassified into the following nine types based on a direction of motionvector MV1 in a horizontal direction and a vertical direction. A symbol(0, 0) indicates that there is not a motion in the horizontal directionand the vertical direction. A symbol (+, 0) indicates that there is amotion in a right direction and there is not a motion in the verticaldirection. A symbol (−, 0) indicates that there is a motion in a leftdirection and there is not a motion in the vertical direction. A symbol(0, +) indicates that there is not a motion in the horizontal directionand there is a motion in an upward direction. A symbol (0, −) indicatesthat there is not a motion in the horizontal direction and there is amotion in a downward direction. A symbol (+, +) indicates that there isa motion in the right and upward directions. A symbol (+, −) indicatesthat there is a motion in the right and downward directions. A symbol(−, +) indicates that there is a motion in the left and upwarddirections. A symbol (−, −) indicates that there is a motion in the leftand downward directions.

The motion vector state determiner 3 classifies motion vectors MV1 intothe nine types (0, 0) to (−, −) for every detection unit, and sums thenumber of motion vectors for each type. Thereby, the motion vector statedeterminer 3 can determine whether or not motion vectors MV1 in oneframe appear in a relatively uniform direction or different directions.For example, the motion vector state determiner 3 generates a statedetermination value that represents a degree of uniformity or variationof directions of motion vectors MV1 in one frame by a predeterminedfunction using the summation of the number of motion vectors for eachtype. The state determination value has one of eight-level of “0” to “7”as well as the first example, and is defined as a determination signalD1. That is, in the second example, the determination signal D1 whichrepresents a distribution state of motion vector MV1 in one frame isgenerated with consideration of a direction of motion vector MV1. Thestate determination value increases as the degree of uniformity ofdirections of motion vectors MV1 increases. A large state determinationvalue indicates that the motion vectors MV1 stabilize.

Next, the configuration and operation of the motion vector corrector 4will be described. As shown in FIG. 4, the motion vector corrector 4includes a motion vector value suppressing part 41 and a motion vectorvalue converting part 42. The determination signal D1 is input into themotion vector value suppressing part 41 and the motion vector valueconverting part 42. When the magnitude of motion vector MV1 exceeds apredetermine value (first threshold), the motion vector valuesuppressing part 41 suppresses the magnitude of motion vector MV1 andoutputs it as a motion vector MV2.

FIG. 5 shows characteristics in a state where the motion vector valuesuppressing part 41 suppresses the magnitude of motion vector MV1. Themotion vector value suppressing part 41 sets the motion vector MV1 as amotion vector MV2 within a range in the magnitude of motion vector MV1from “0” to the first threshold S, and when it exceeds the firstthreshold S, generates a motion vector MV2 according to the followingequation (1).MV2=MV1×m/n+s×{(n−m)/n}  (1)

In the equation (1), variables m and n are predetermined natural numberswhich have the relation of m<n, and these values are arbitrarily set.Although the first threshold S, that is a position which is a startpoint at which the motion vector MV1 starts to decrease, may be fixed,it is preferable to vary the first threshold S according to the statedetermination value of the motion vector MV1. It is further preferableto increase the first threshold S as the state determination valueincreases.

The motion vector MV2 is input into the motion vector value convertingpart 42. FIG. 6 shows characteristics in a state where the motion vectorvalue converting part 42 converts the magnitude of motion vector MV2.The motion vector value converting part 42 sets the motion vector MV2,which is not changed, as a motion vector MV3 within a range in themagnitude of motion vector M2 from “0” to a second threshold r. Themotion vector value converting part 42 holds the motion vector MV3 to aconstant value r within a range in the magnitude of motion vector MV2from the second threshold r to a third threshold t. When the magnitudeof motion vector MV2 exceeds the third threshold t, the motion vectorvalue converting part 42 generates a motion vector MV3 according to thefollowing equation (2).MV3=2×r+h−MV2  (2)

According to the equation (2), the magnitude of motion vector MV3decreases at a predetermined rate to approach “0” when the magnitude ofmotion vector MV2 exceeds the third threshold t. Although the secondthreshold r and the range h between the second threshold r and the thirdthreshold t may be fixed, it is preferable to vary them according to thestate determination value of the determination signal D1. It is furtherpreferable to increase the second threshold r and the range h as thestate determination value increases. Alternately, while the range h isfixed, the second threshold r may be increased as the statedetermination value increases.

FIGS. 7 to 9 show correction characteristics in respective states wherethe motion vector corrector 4 corrects the motion vector MV1 to themotion vector MV3 by conversion process according to the equations (1)and (2). FIG. 7 shows correction characteristics in a case where thevariables m and n are “3” and “4”. FIG. 8 shows correctioncharacteristics in a case where the variables m and n are “1” and “2”.FIG. 9 shows correction characteristics in a case where the variables mand n are “1” and “4”. As can be seen from FIGS. 7 to 9, as a slopedetermined by a conversion feature of the equation (1) in a region wherethe magnitude of motion vector MV1 exceeds the first threshold s getsgentle (magnitude of slope is decreased), a negative slope determined bya conversion feature of the equation (2) in a region where the magnitudeof motion vector MV1 exceeds the range h becomes gentle (degree ofdecrement becomes small).

By correction operations shown in FIGS. 7 to 9 for motion vector MV1 bythe motion vector corrector 4, when a degree of motion is large, themotion vector MV3 to be actually used in the interpolated pixel datagenerator 5 is converged on “0” corresponding to a still vector. Thisreduces a feeling of visual strangeness in an interpolated image(failure of interpolated image) even when a false detection occurs inthe motion vector detector 2. When a motion vector is relatively small,the motion vector 1 is not corrected and is set as a motion vector 3.Thus, if a degree of motion is normal, a good interpolated image can begenerated.

In the present embodiment, since the range h where the motion vector MV3has the constant value r is set as the characteristics of motion vectorMV3, a state where the motion vector MV1 is not corrected by the motionvector corrector 4 is smoothly changed into a state where the motionvector MV1 is corrected. This reduces a feeling of visual strangeness inan interpolated image.

The present invention is not limited to the present embodiment describedabove, and various changes may be made without departing from the scopeof the invention. The present invention includes programs for causing acomputer to realize functions of elements described in the presentembodiment. These programs may be read from a recording medium and thenloaded in the computer, or be transmitted via a communication networkand then loaded in the computer.

REFERENCE SIGNS LIST

-   1 frame memory-   2 motion vector detector-   3 motion vector state determiner-   4 motion vector corrector-   5 interpolated pixel data generator-   6 frame frequency converter-   41 motion vector value suppressing part-   42 motion vector value converting part

The invention claimed is:
 1. A motion vector correction devicecomprising: a circuitry that detects, using pixel data in at least tworeal frames in an input video signal, a first motion vector necessaryfor generating interpolated pixel data forming an interpolated frame tobe inserted between the two real frames, and corrects the first motionvector to decrease the magnitude of first motion vector when themagnitude of first motion vector exceeds a first threshold, wherein whenthe magnitude of first motion vector exceeds the first threshold, thecircuitry decreases the magnitude of first motion vector within a rangewhere the magnitude of first motion vector is larger than the firstthreshold such that a decrement amount of the magnitude of first motionvector increases as a value between the magnitude of first motion vectorand the first threshold increases, and outputs the result as a secondmotion vector, when the magnitude of second motion vector exceeds asecond threshold, the circuitry keeps the magnitude of second motionvector unchanged from the second threshold to a third threshold largerthan the second threshold, and outputs the result as a third motionvector, and when the magnitude of second motion vector exceeds the thirdthreshold, the circuitry decreases the magnitude of second motion vectorwithin a range where the magnitude of second motion vector is smallerthan the second threshold such that a decrement amount of the magnitudeof second motion vector increases as a value between the magnitude ofsecond motion vector and the third threshold increases, and outputs theresult as a third motion vector.
 2. The motion vector correction deviceaccording to claim 1, wherein when the magnitude of second motion vectorexceeds the third threshold, the circuitry calculates the third motionvector according to the following calculus equation2×(the second threshold)+(the third threshold−the second threshold)−(themagnitude of second motion vector).
 3. The motion vector correctiondevice according to claim 1, the circuitry determines an appearancestate of the first motion vector in a screen to generate and output astate determination value, wherein the circuitry varies characteristicsof decrease of the magnitude of first motion vector according to thestate determination value.
 4. The motion vector correction deviceaccording to claim 3, wherein the circuitry generates a statedetermination value that represents an appearance amount of motionvectors indicating how many first motion vectors appear in a screen. 5.The motion vector correction device according to claim 3, wherein thecircuitry generates a state determination value that represents adistribution state of motion vectors indicating a degree of uniformityor variation of directions of first motion vectors in a screen.
 6. Avideo signal processing apparatus comprising: a circuitry that generatesinterpolated pixel data, using pixel data in at least two real frames inan input video signal and a motion vector corrected by the motion vectorcorrection device according to claim
 1. 7. A motion vector correctiondevice comprising: a circuitry that detects, using pixel data in atleast two real frames in an input video signal, a first motion vectornecessary for generating interpolated pixel data forming an interpolatedframe to be inserted between the two real frames, and corrects the firstmotion vector to decrease the magnitude of first motion vector when themagnitude of first motion vector exceeds a first threshold, wherein whenthe magnitude of first motion vector exceeds the first threshold, thecircuitry decreases the magnitude of first motion vector within a rangewhere the magnitude of first motion vector is larger than the firstthreshold such that a decrement amount of the magnitude of first motionvector increases as a value between the magnitude of first motion vectorand the first threshold increases, and outputs the result as a secondmotion vector, when the magnitude of second motion vector exceeds asecond threshold, the circuitry keeps the magnitude of second motionvector unchanged from the second threshold to a third threshold largerthan the second threshold, and outputs the result as a third motionvector, and when the magnitude of second motion vector exceeds the thirdthreshold, the circuitry decreases the magnitude of second motion vectorwithin a range where the magnitude of second motion vector is smallerthan the second threshold such that a decrement amount of the magnitudeof second motion vector increases as a value between the magnitude ofsecond motion vector and the third threshold increases, and outputs theresult as a third motion vector, and wherein the circuitry calculatesthe second motion vector according to the following calculus equationthe magnitude of first motion vector)×m/n+the first threshold)×(n−m)/n,where variables m and n are natural numbers which have a relation ofm<n.
 8. The motion vector correction device according to claim 7 whereinwhen the magnitude of second motion vector exceeds the third threshold,the circuitry calculates the third motion vector according to thefollowing calculus equation:2×(the second threshold)+(the third threshold−the second threshold)−(themagnitude of second motion vector).
 9. The motion vector correctiondevice according to claim 7, the circuitry determines an appearancestate of the first motion vector in a screen to generate and output astate determination value, wherein the circuitry varies characteristicsof decrease of the magnitude of first motion vector according to thestate determination value.
 10. A video signal processing apparatuscomprising: a circuitry that generates interpolated pixel data, usingpixel data in at least two real frames in an input video signal and amotion vector corrected by the motion vector correction device accordingto claim
 7. 11. A motion vector correction method comprising: a motionvector detection step for, using pixel data in at least two real framesin an input video signal, detecting a first motion vector necessary forgenerating interpolated pixel data forming an interpolated frame to beinserted between the two real frames; and a motion vector correctionstep for correcting the first motion vector to decrease the magnitude offirst motion vector when the magnitude of first motion vector exceeds afirst threshold, wherein the motion vector correction step includes: amotion vector value suppressing step for decreasing, when the magnitudeof first motion vector exceeds the first threshold, the magnitude offirst motion vector within a range where the magnitude of first motionvector is larger than the first threshold such that a decrement amountof the magnitude of first motion vector increases as a value between themagnitude of first motion vector and the first threshold increases, andoutputting the result as a second motion vector; and a motion vectorvalue converting step for keeping, when the magnitude of second motionvector exceeds a second threshold, the magnitude of second motion vectorunchanged from the second threshold to a third threshold larger than thesecond threshold, and outputting the result as a third motion vector,and decreasing, when the magnitude of second motion vector exceeds thethird threshold, the magnitude of second motion vector within a rangewhere the magnitude of second motion vector is smaller than the secondthreshold such that a decrement amount of the magnitude of second motionvector increases as a value between the magnitude of second motionvector and the third threshold increases, and outputting the result as athird motion vector.
 12. The motion vector correction method accordingto claim 11, wherein when the magnitude of second motion vector exceedsthe third threshold, the motion vector value converting step calculatesthe third motion vector according to the following calculus equation2×(the second threshold)+(the third threshold−the second threshold)−(themagnitude of second motion vector).
 13. The motion vector correctionmethod according to claim 11, further comprising a motion vector statedetermination step for determining an appearance state of the firstmotion vector in a screen to generate a state determination value,wherein the motion vector correction step varies characteristics ofdecrease of the magnitude of first motion vector according to the statedetermination value.
 14. The motion vector correction method accordingto claim 13, wherein the motion vector state determination stepgenerates a state determination value that represents an appearanceamount of motion vectors indicating how many first motion vectors appearin a screen.
 15. The motion vector correction method according to claim13, wherein the motion vector state determination step generates a statedetermination value that represents a distribution state of motionvectors indicating a degree of uniformity or variation of directions offirst motion vectors in a screen.
 16. A video signal processing methodcomprising: an interpolated pixel data generation step for generatinginterpolated pixel data, using pixel data in at least two real frames inan input video signal and a motion vector corrected by the motion vectorcorrection method according to claim 11.